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HVACR Tech Tip: How to Clean Evaporator Coils for Preventive Maintenance

Last updated: 07-10-2020

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HVACR Tech Tip: How to Clean Evaporator Coils for Preventive Maintenance

When it’s time to provide your customer's preventive maintenance don’t forget to pay particular attention to system components that are out of sight within the system cabinet or air handler enclosure. The unit’s evaporator coils are among the more important of these hidden components. Problems can develop with dirty evaporator coils as it can affect the system's performance and efficiency. This can also lead to damage and/or breakdowns. Here is some basic information on effectively cleaning evaporator coils.

Evaporator coils are probably the most difficult to clean. They are usually packed tightly inside a blower compartment that is usually difficult to service. They may be located over bathtubs, in tight dark closets, on rooftops in commercial applications, in a hot attic or a myriad of other places that are usually cramped, dark and uncomfortable. Due to these inconveniences, evaporator coils are often left alone and not cleaned until a system problem emerges. An evaporator coil should be inspected every six months and may need to be cleaned every six months to four years, depending on environment and filtration.

Make sure to disconnect the power to the unit while cleaning the coil. This will prevent a potential electrical hazard. Disassemble the unit to the extent that both sides of the coil can be accessed. For applications that have matted hair and dirt on the intake side of the coil, it is important that they be carefully brushed clean. Failure to do so will severely limit the penetration of the coil cleaner and dramatically reduce its effectiveness. There are several disposable types of coil brushes available from different manufacturers that do a very good job of cleaning the surface dirt off while keeping your hands away from the filth and fins. One note of warning - the fins on a/c coils are very sharp and can cause severe cuts to skin. Be sure to avoid contact with the coil with your hands, arms, etc. It’s advisable to wear gloves, face mask and apron during this procedure since potential organisms growing on the coil and contact with lungs, skin, eyes or clothing may transmit disease.

Once the surface dirt has been removed, a good evaporator coil cleaner, such as Acti-Klean should be mixed in a low-pressure sprayer with water in a dilution ration of between 3:1 to 1:1, depending on the condition of the coil and the type of dirt encountered. Acti-Klean is a concentrated set of soaps and surfactants (wetting agents that help the cleaner penetrate the coil fully). The coil should then be sprayed liberally from both sides of the coil with the coil cleaner solution. This coil cleaner will not create the foam that condenser coil cleaners do, so don’t be shy applying the coil cleaner. Make sure that the liquid does not fall onto electrical components in the system. The cleaner will cut through grease and oils, as well as dislodge any dirt, dust, and hair that may be trapped in the coil and rinses them down the condensate drain. An alternative option would be Virginia Coil Klean aerosol coil cleaner. This product will foam out dirt and dust and is certainly more convenient in the aerosol container, although it is more costly than cleaners like Acti-Klean. When the coil is clean, it is recommended that where possible the coil be rinsed off. This will aid in removing any remaining dirt from the coil. If this is not possible, then the condensate created by running the a/c system will rinse off any remaining cleaner. Depending on temperature and humidity conditions, the unit should run for between 15 minutes to 1 hour to ensure all cleaner is rinsed off the coil.

In recent years, indoor air quality has received a lot of attention. Often a case of “black mold” in some air conditioning system is reported in the news and the entire building must be evacuated and sanitized. It is a good idea after cleaning the coil that an EPA registered bacteriostat be used on the coil and surrounding ductwork and insulation to ensure that any minor growths and odors are eliminated. Doing so provides your customer with a valuable service by ensuring that mold and other growths do not develop throughout the system. It is important the technician pays close attention to the volume of dirt and other growths coming off the coil. It is not uncommon for release dirt to block the opening of the condensate drain line and restrict the draining of water. If this is observed, the blockage should be removed before the drain pan overflows.

While cleaning the coil, it is a good time to clean the drain pan as well. Simply clean out any rust and deposits that may be sitting in the bottom of the pan with a towel, rag or other means. Once again, be careful not to rub your hand across the coil as the edges are quite sharp. Protective gloves are recommended.

For more information see Catalog G-1.

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